Table 2. Direct Microwave Heating of Resin-Coated Sand Using Heat From Microwave-Absorbing Ceramics to Permit Direct Hybrid Processing
Fig. 4. This reclaimer unit was installed at Midwest Metal Products with 4-degree feed angle incorporated into the leg structure.
Bake Time Initial Weight (g) 1 min. 2 min. 3 min. 4 min. 5 min. 6 min. 7 min. 8 min.
32.968 32.260 21.305 22.961 54.226 40.844 37.627 55.290
remove as much volatile resin material within three minutes as opposed to microwave and hot air. Te technique reported in Table 2 is essentially a static and batch version on the microwave prototype, where the sand material is constantly in contact with hot surfaces and exposed to microwave energy. Table 3 reports the initial data
from the prototype microwave rotary unit. What is shown is the set-point temperature of the unit (air tem- perature), the temperature of the sand immediately as it emerges from the output section (measured using IR pyrometer), the prototype rotation speed (as a percentage of maximum) the estimated dwell time (from start of sample flow from the storage bin to the leading edge of the sand as it exits the unit) and LOI. As reported in Table 3, sand
temperatures are lower than the set- point temperatures because sand is
Final Weight (g) Weight Lost (g) 32.915 32.170 21.173 22.702 53.636 40.513 37.250 54.740
0.053 0.090 0.132 0.259 0.590 0.331 0.377 0.550
Table 3. Initial Data From the Microwave Rotary Unit Sand Exit
Set Air Temperature (oC/oF)
1 2 3 4 5
725/1337 725/1337 700/1292 525/977 525/977
Temperature (oC/oF) 380/716 680/1256 290/554 200/392
175-200/347-392
not capable of absorbing microwave energy at these temperatures, so it’s relatively transparent. Te resins and other materials are impacted by microwave and begin to burn off as soon as these materials enter the process zone or hot zone. Visual inspection of the sand once
it strikes the collection bin shows it continually becomes lighter in color as it cools in the collection bin. Tis is believed to be resin that didn’t have the residence time to burn-off completely within the unit (given the maximum output power is 10kW)
% Lost 0.16% 0.28% 0.62% 1.13% 1.09% 0.81% 1.00% 0.99%
Trial Speed
15 35 25 15 25
Dwell Time (min)
8 4 7 8 7
LOI 0.01
0.01 0.01 0.05 0.09
and continued to burn off as it sat in the collection bin. If the power level was higher, more energy would be available to aid in burn off at that residence time. Te photographs in Fig. 5-7 show
microwave is capable of reclaiming sand and using air temperatures of 977F (525C) give an LOI of less than 0.1 with the measured sand tempera- ture of around 392F (200C). This was the minimum tempera-
ture condition attempted, and work is continuing on throughput and rate information.
Fig. 5. Shown is a sample of waste sand with no reclamation technique attempted.
Fig. 6. LOI on the sand that was mechani- cally reclaimed using a rotary mechanical reclaimer at MMP was about 1.44.
Fig. 7. This sample was reclaimed in the microwave rotary system from condition set 1, as described in Table 3. The LOI was 0.01. Dark areas are magnetite.
April 2016 MODERN CASTING | 39
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55 |
Page 56 |
Page 57 |
Page 58 |
Page 59 |
Page 60